The heart is at the center of the circulatory system. It includes four chambers—two atria and two ventricles. The right atrium receives deoxygenated blood from the body, pumps it into the right ventricle, and the right ventricle pumps the blood to the lungs to be re-oxygenated. The re-oxygenated blood returns to the left atrium, it is pumped into the left ventricle, and then the blood is pumped by the left ventricle throughout the body to meet the hemodynamic needs of the body.
Heart sounds are associated with mechanical vibrations from activity of a patient's heart and the flow of blood through the heart. Heart sounds recur with each cardiac cycle and are separated and classified according to the activity associated with the vibration. The first heart sound (S1) is the vibrational sound made during closure of the mitral and tricuspid valves. The second heart sound (S2) is made by the closure of the aortic and pulmonary valves. The third heart sound (S3) and fourth heart sound (S4) are often related to abnormal filling pressures of the left ventricle during diastole. Heart sounds are useful indications of proper or improper functioning of a patient's heart.
Implantable medical devices (IMDs) are devices designed to be implanted into a patient. Some examples of these devices include cardiac function management (CFM) devices such as implantable pacemakers, implantable cardioverter defibrillators (ICDs), cardiac resynchronization devices, and devices that include a combination of such capabilities. The devices are typically used to treat patients using electrical therapy or to aid a physician or caregiver in patient diagnosis through internal monitoring of a patient's condition, or both. The devices may include or be connected to electrodes in communication with circuitry to monitor electrical heart activity within a patient, and often include one or more other sensors to internally monitor other patient parameters. Other examples of implantable medical devices include implantable diagnostic devices, implantable insulin pumps, devices implanted to administer drugs to a patient, or implantable devices with neural stimulation capability.